Ahh - That's an intriguing use for these adapters. You'll likely want to contact OP directly with that inquiry. (I looked on the usual SNES board databases, but it's unclear to me if the maskroms are the same between SuperFX boards and MM X2/X3 boards.)

Oh, I must've been looking at the DIP pinout instead of comparing TSOP pinouts.
If you program the flash chip before mounting it on the adapter and tie the /WE pin to +5v then there'd be no problem.
But that flash chip goes only up to 4mbit which isn't very useful as most (all?) superfx games are larger than that.

Unfortunate that 5V flash in the right capacities (8m, 16m and up) don't seem to be common. And places like mouser and digikey dont carry these EPROMs anymore (labeled "Obsolete")
Too bad some sort of MicroSD card board doesn't exist that could be retrofitted onto SuperFX carts. Like a Micro-Everdrive daughterboard that could take the place of the mask rom (lol wishful thinking!).